Protection of converters

ABSTRACT

A process for the protection of converter mouths and, more particularly, to an improved process for protecting the metal and refractory lining at the mouth of a converter by applying about the converter mouth prior to operating the converter a coating which comprises a mixture of a ceramic material and sodium silicate.

AU 112 Ex inventor William H. Foard 1,906,557 5/1933 Evans I 75/72 Inspiration, Ariz. 2,162,387 6/1939 Radabaugh. 106/84 X Appl. No. 26,071 2,232,162 2/ 1 941 Boller 106/84 X Filed Apr. 6, 1970 2,415,165 2/1947 Daussan 266/43 X Patented Jan. 11, 1972 2,499,729 3/1950 Daussan 106/84 X [73] Assignee Inspiration Consolidated Copper Company 3,006, 10/ 1 961 Shephard 26 /43 X Inspiration, Arlz. 3,229,970 1/1966 Henry 266/43 Primary Examiner-L. Dewayne Rutledge Assistant Examiner-Jose h E. Le ru 54 PROTECTION F v P 8 l 1 6 Claims No g f g ERTERS Anarney- Pennie, Edmonds, Morton, Taylor and Adams [52] US. Cl 75/72, 106/84, 266/43 51 Int. Cl l. 2 I l C ABSTRACT: A process for the protection of converter Field ofSearchmr. /72 74- mm paflcularly' Pmess a protecting the metal and refractory lining at the mouth of a converter by applying about the converter mouth prior to [56] Refe en (m d operating the converter a coating which comprises a mixture UNITED STATES PATENTS of a ceramic material and sodium silicate. 832,895 10/1906 Charles 75/72 X k I- i PROTECTION OF CONVERTERS This invention relates to a process for the protection of converter mouths and, more particularly, to an improved process for protecting the metal and refractory lining at the mouth of a converter by applying about the converter mouth prior to operating the converter a coating which comprises a mixture of a ceramic material and sodium silicate.

One of the difficult problems encountered during the operation of a converter has been the removal of metallic accretions from the mouth of the converter. For example, during the conversion of copper matte to blister copper, large volumes of air are blown into the bath through tuyeres submerged beneath the surface of the bath. Flux is also added to the bath to combine with the iron oxidized from the matte in the form of an iron silicate slag. As the blowing process progresses, substantial quantities of matte, magnetite, slag, white metal, and copper are expelled from the molten bath and solidify about the converter mouth when the resulting accretions adhere tenaciously to both the steel and the masonry of the converter structure. These accretions build up to a point at which they interfere with the operation of the converter. To prevent this interference, these accretions are usually removed by pulling them from the converter mouth with the use of a crane hook. This procedure often results in a substantial amount of damage to the converter mouth. Since the metallic accretions adhere to the mouth of the converter, these accretions usually break in pieces as they are pulled, and parts of the metal shell and masonry lining adjacent the mouth of the converter may be bent or broken. The end result is that the converter must be shut down from time to time in order to repair such damage.

Conventionally, converter mouths have been protected from this sort of damage by the manual application of a plastic mud on the mouth lining. in some operation, refractory metal lips or steel coated with a refractory metal have been used to protect the converter mouth. However, the manual application of mud is a hazardous and tedious operation and the use of refractory metals on the converter mouth involves the use of expendable and expensive materials.

It is, therefore, the principal object of this invention to over come the disadvantages stated hereinabove by providing an improved process for protecting the mouths of converters from damage incident to the removal of mouth accretions, which process includes coating the mouth of the converter with a slurry formed of a mixture of a ceramic material and sodium silicate, and thereby to overcome the shortcomings and inadequacies of the prior art methods while preventing damage to the converter mouths.

The present invention contemplates a fast, inexpensive, and efficient process for protecting the metal and refractory lining at the mouth of a converter so as to prevent substantially any damage thereto upon removal of accretions therefrom. In the operation of a copper converter wherein during the normal cycle of converter operation a heavy accretion mixture of solidified matte, slag, white metal, magnetite, and copper forms on the converter shell and lining about the mouth thereof, the present invention consists of an improvement which comprises spraying on the converter shell and lining about the mouth while it is free of accretions a coating of substantial thickness consisting essentially of a slurry of finely divided ceramic material in an aqueous solution of sodium silicate, allowing such coating to dry and harden, subsequently operating the converter norm ally until substantial solid accretions have built up over the dried and hardened coating, and then pulling said accretions from about the converter mouth, the coating serving to prevent firm adhesion of the accretions and to facilitate removal of the accretions without damage to the converter structure.

A very significant advantage which results from the improved process is that the accretion collars which form at the converter mouth are easy to pull off, and frequently come off in one piece as large rings without any damage to the converter mouth whatsoever. in addition to practically eliminating damage to the metal and refractory lining adjacent the converter mouth, the total time consumed in coating the converter mouth and pulling off the collar is substantially less than that previously required in crane time simply for pulling off the collar in pieces.

Substantially, any type of ceramic material may be used in the improved process of the present invention. For example, silica sand or any of numerous ceramic fire clay compositions may be used. Also, ceramic compositions containing aluminum silicate and/or other refractory silicates as major constituents may be used. It has been discovered that flotation tailings, for example, the flotation tailings from a copper sultide flotation process, which contain a high percentage of silica and various silicates, can be used. lndeed, any ceramic material which when mixed with sodium silicate and sprayed about the converter mouth forms a refractory parting layer having low mechanical strength properties between the materials of the converter mouth and the metallic accretions can be used with success.

In preparing the coating composition in accordance with the invention, a slurry is first formed from a mixture of a finely divided ceramic material and water. This slurry should contain approximately 40 to 60 percent by volume of the ceramic material. The protective coating composition contains, in addition to the ceramic material, a binder of sodium silicate. This binder is prepared by mixing the sodium silicate with water in such proportion so that a solution having a somewhat syrupy consistency is obtained. A suitable binder solution may consist of commercial water glass (approximately a 30 percent by weight sodium silicate aqueous solution) or it may be commercial water glass diluted with up to about five parts by volume of water, so that the aqueous binder contains approximately 5 to 30 percent by weight of sodium silicate. The ceramic slurry is then mixed with approximately 5 to 10 percent by volume of the syrupy sodium silicate to supply about one part by weight of sodium silicate to about five to parts by weight of ceramic material. This mixture is placed in a conventional spray gun apparatus, such as, a spray gun of the type used to apply refractory material to metallurgical furnaces, and the mixture is sprayed on to the lining and shell at the mouth of the converter. The coating can be applied to substantially any desired thickness, the basic requirement being that the metal shell and masonry lining surrounding the converter mouth be coasted with the protective mixture. A coating thickness of from one-eighth inch to 1 inch has been found to be eminently suitable. The mixture is then allowed to dry or cure so that a hardened refractory coating is formed.

The invention will be described in detail with reference to the following example for illustrative purposes.

EXAMPLE A 13 by 23 foot Peirce-Smith converter was being used for the conversion of copper matte to blister copper. The metal shell and masonry lining about the mouth of the converter were sprayed, using a conventional spray gun of the sort used for repairing reverberatory furnace roofs with a ceramic slurry. The slurry was a mixture of finely divided fire clay and water (approximately 50 percent by volume solids) to which was added 5 percent by volume of commercial water glass (about 30 percent by weight sodium silicate). This slurry was sprayed about the mouth of the converter until a coating having a thickness which varied from one-half to three-fourth inch was formed. The sodium silicate addition resulted in rapid airsetting of the slurry, and in only a short time the ceramic coating was firmly adherent to the lining at the converter mouth. After the coating had dried, the converter was placed in operation. During the converter operation, the usual large quantities of copper, slag, magnetite, etc., built up an accretion over the coating surrounding the mouth of the converter. After a substantial buildup of a collar of such accretions had formed, a crane hook was placed in position to pull the collar from the converter. Without any difficulty, the collar was removed as a single large ring. A close inspection of the converter mouth showed that the ceramic coating prevented any damage to either the metal or masonry lining at the converter mouth. The converter was then sprayed with a further coating of the ceramic slurry to prepare it for the next cycle of operation.

lclaim:

1. In the operation of a copper converter wherein during the normal cycle of converter operation a heavy accretion mixture of solidified matte, slag, white metal, magnetite, and copper forms on the converter shell and lining about the mouth thereof, the improvement which comprises spraying on the converter shell and lining about the mouth while it is free of accretions a coating of substantial thickness consisting essentially of a slurry of finely divided ceramic material in an aqueous solution of sodium silicate, allowing such coating to dry and harden, subsequently operating the converter normally until substantial solid accretions have built up over the dried and hardened coating, and then pulling said accretions from about the converter mouth, the coating serving to prevent firm adhesion of the accretions and to facilitate removal of the accretions without damage to the converter structure.

2. The improved process according to claim 1 in which the ceramic is fire clay.

3. The improved process according to claim I in which the ceramic comprises siliceous flotation tailings from a flotation process.

4. The improved process according to claim 3 in which the flotation tailings are from a copper sulfide flotation process.

5. The improved process according to claim 1 in which the mixture contains sodium silicate in an amount of about 5 percent to 10 percent by volume.

6. The improved process according to claim I in which the coating is applied to a thickness in the range from about oneeighth inch to about 1 inch.

1! i I i 

2. The improved process according to claim 1 in which the ceramic is fire clay.
 3. The improved process according to claim 1 in which the ceramic comprises siliceous flotation tailings from a flotation process.
 4. The improved process according to claim 3 in which the flotation tailings are from a copper sulfide flotation process.
 5. The improved process according to claim 1 in which the mixture contains sodium silicate in an amount of about 5 percent to 10 percent by volume.
 6. The improved process according to claim 1 in which the coating is applied to a thickness in the range from about one-eighth inch to about 1 inch. 